SEOUL, South Korea — The military is gearing up to practice one of its worst nightmare scenarios in South Korea — a mass evacuation — next month even as officials work to update plans for moving hundreds of thousands of civilians off the peninsula in case of war.

The semiannual rehearsal, known as Focused Passage, is scheduled for April 16-20. That will make April a busy month on the divided peninsula since the noncombatant evacuation operation will occur at the same time as joint war games with the South.

The military holds evacuation exercises every spring and fall, involving mostly family members and civilian contractors. It will transport a group of about 100 volunteers all the way to the United States this year in what is believed to be a first, people familiar with the plan told Stars and Stripes.

This year’s NEO will take place at a sensitive time. North Korean leader Kim Jong Un is expected to hold historic summits with South Korean President Moon Jae-in in late April and with President Donald Trump in May.

Heightened tensions over Pyongyang’s nuclear weapons program have served as a wakeup call for NEO organizers as the possibility of conflict rose last year with several missile tests by the North and threats of military action by both sides.

The situation has calmed after North Korea’s participation in the Winter Olympics last month led to a series of diplomatic breakthroughs. But U.S. officials and experts said there’s a new awareness about the need to be ready for the worst-case scenario.

Adm. Harry Harris, the head of the Hawaii-based Pacific Command, said during a House Armed Services Committee hearing last month that Army Pacific at Fort Shafter has been tasked with updating the evacuation plan for South Korea.

Harris was responding to a question by Rep. Anthony Brown, D-Md., who expressed concern about flaws in the current plan.

“I don’t get the sense that the rehearsals, the walkthroughs, the soup to nuts had been thought through logistically,” Brown, a retired Army Reserve colonel, said.

He noted the evacuation would likely be happening at the same time additional troops were flowing onto the peninsula. Harris acknowledged that “there is work to be done.”

“If conflict breaks out on the Korean Peninsula then we’re going to have to get Americans off of there. The numbers are staggering,” he said, giving estimates of 200,000-plus American civilians in addition to more than 1 million Chinese and 60,000 Japanese who would also be looking for a way out.

“Our friends, allies, partners and others also have a vested interest in the evacuation of noncombatants should war break out on the peninsula,” Harris told lawmakers at the Feb. 14 hearing without elaborating.

NEO under scrutiny

The State Department has the overall responsibility for noncombatant evacuations, but the military would carry them out.

That means carrying out exercises on a routine basis to examine everything from the tactical level, such as assembly points, to operational and strategic aspects, Army Pacific spokesman Col. Christopher Garver said.

“The plans needed an update because the scope and scale of the situation continues to grow and because the war plans themselves have evolved over time,” he said Thursday in an email.

The issue has taken on urgency as North Korea demonstrated rapid progress toward its goal of developing a nuclear weapon that could reach the U.S. mainland.

It test-fired several missiles last year that appeared to be within reach of U.S. bases in South Korea, Japan and possibly Guam, although experts are divided over how close it is to perfecting the technology needed to actually strike.

Trump responded by mocking Kim as “little rocket man” and threatening to unleash “fire and fury” and to “totally destroy North Korea” if necessary to defend the U.S. and its allies.

In December, Sen. Lindsey Graham, R-S.C., said it was getting too dangerous to keep noncombatants in South Korea and even suggested making the country an unaccompanied post, meaning servicemembers could not bring family with them.

The U.S. military quickly said it has no plans to initiate evacuations while saying the safety and welfare of troops, civilian staff and loved ones are top priorities and contingency plans are in place.

The Financial Times reported that officials vetting Korea expert Victor Cha as a possible nominee to be the U.S. ambassador in Seoul asked if he was prepared to help manage the evacuation of American citizens, a move that would almost certainly send a signal to the North that military action was imminent.

Cha later cited the dangers facing Americans as he expressed reservations about a military strike in an op-ed in The Washington Post.

“Given that an evacuation of so many citizens would be virtually impossible under a rain of North Korean artillery and missiles (potentially laced with biochemical weapons), these Americans would most likely have to hunker down until the war was over,” he wrote.

Testing capabilities

The drills, Focused Passage in the spring and Courageous Channel in the fall, are mainly aimed at testing plans and making sure family members of troops and civilians working for the military are ready to go at a moment’s notice.

The process appears orderly as spouses and children with backpacks and go-bags file through stations set up in gyms and other assembly points on the main U.S. bases. Soldiers check their information packets and staff from the Red Cross and other departments are on hand to answer questions about pets, vehicles and other concerns.

Yongsan Garrison offered free helicopter rides to encourage participation last year. A select group was flown to Yokota Air Base in western Tokyo.

This year about 100 people will travel all the way to the United States, according to people familiar with the call for volunteers. All spoke on condition of anonymity because they weren’t authorized to release the information.

He also dismissed concerns that Focused Passage will coincide this year with the joint war games known as Foal Eagle and Key Resolve, which were delayed until after the Olympics and Paralympics, which ended March 18.

Experts warn the reality would be chaos, with millions of Koreans and foreigners streaming south. A key uncertainty is what will happen with the hundreds of thousands of non-military Americans in South Korea, including tourists.

“The drills are probably a 10th of a percent of the people or less who would be moving,” said Bruce Bennett, a Rand Corp. defense analyst who was in Seoul this week. “The other thing to remember is that we’re moving just Americans in the drills and in practice we’d be moving multiple nationalities, including likely the Japanese.”

“You’d have to move through a Korea where many Koreans would also be moving to get out,” Bennett said, adding that the Chinese would also be rushing to buy up space in planes and ferries to get their people out. “We would require some major coordination.”

He said North Korean missiles also could threaten air bases and assets needed to lift people off the peninsula and pointed out that any plan to take people first to nearby bases in Japan would be complicated by political concerns as Tokyo would have to worry about its own people in South Korea.

“The bottom line is that they discovered that they had a plan which was in trouble, which was not in great shape,” he said.

The U.S. Embassy doesn’t provide details about evacuation plans but “encourages all U.S. citizens traveling to or residing in Korea to register” with the Smart Traveler Enrollment Program known as STEP, which can be done online. It notes the consular section’s website also has relevant information.

An actual NEO would ideally be the last step. The first thing to watch for would be an authorized departure for American citizens, which would be announced to allow people to leave by commercial means, officials said.